Design Of Magnetic Components Research Articles

An LLC and LCL-T Resonant Tanks Based Topology for Battery Charger Application

To achieve the constant current (CC) and constant voltage (CV) charge of the lithium battery, the traditional LLC resonant converter requires the switching frequency varies in a wide range, which brings difficulty to the magnetic components design, and the system efficiency would also be degraded. In this article, a novel topology based on LLC and LCL-T resonant tanks is proposed to reduce the range of operating switching frequency. During the CC charge state, the proposed converter is operating with the LCL-T resonant tank, and it can be regarded as a current source, which provides constant charging current to the battery. During the CV charge state, the LCL-T resonant tank is bypassed and the structure of the proposed converter is modified to a traditional LLC resonant converter, and it is functioning as a CV source. Owing to the high accuracy of the CC and voltage sources, the required operating switching frequency range can be significantly reduced when compared with traditional LLC approaches. Operational principles and design guidelines for the proposed converter are described. Experiment and simulation results from a 180 W prototype are provided to validate the theoretical analysis.

Split Duty Cycle Coupled Multiphase Boost–Buck Converter

The classic boost and buck cascaded converter has inductors at the input and output ports of the converters, which makes it ideal interface for bidirectional battery charging applications where accurate current control and low ripple currents are required. This paper proposes a split duty cycle coupled multi-phase variant applied to the cascaded boost-buck converter and utilizing coupled inductor features to achieve very lower current ripples at the output,lower power losses, reduction in magnetic component volume. Moreover, current sharing between each phase is inherently implemented, making it suitable for high conversion ratio bidirectional operation in a systematic energy storage applications where the low voltage port has very high current. The paper covers split duty cycle converter operation principle using coupled inductors between input and the multi-phase output. Magnetic component design and selection guidelines are presented. The proposed control method and coupled inductor structure are validated by simulation and experimental results.

Thermal Design, Optimization, and Packaging of Planar Magnetic Components

This article is focused on the thermal design and three-dimensional (3-D) package optimization of planar magnetic components (PMCs), including transformers and inductors for application in an electric vehicle composite boost dc-dc converter. Each PMC comprises electrical windings in printed circuit board (PCB) form in combination with a ferrite core. Multiple features of each PMC package are thermally optimized for the proposed device configurations with given core size, core loss distribution, number of turns in the PCB winding, winding copper thickness, and winding loss distribution. These heuristically optimized features include a lower level cold plate structure with a conformal base for enhanced convective heat transfer, an upper level PMC cap structure for doubled-sided cooling through conductive heat flow to the cold plate, the implementation of functionally distributed copper thermal and electrothermal vias in the PCB winding for improved cross-plane thermal conductance, and judicious implementation of select materials at various locations and interfaces within the package. Detailed numerical modeling reveals the combined effect of this 3-D packaging strategy with a 79.3 °C and 48.5 °C maximum temperature reduction in the core and PCB winding, respectively, relative to a baseline device configuration. Select PMC experimental validation confirms the expected thermal performance of an optimized PCB design. The thermal design approach is relevant for a range of high-power-density electronics PMC packaging applications.

Magnetic moment configuration: One of decisive factors to enhance the optical mode resonance in interlayer exchange coupled trilayers

The optical mode (OM) ferromagnetic resonance (FMR) pushes the frequency of soft magnetic films from 10 to 20 GHz, showing a great engineering application prospect in monolithic microwave integrated circuits. However, the determinants of OM frequency and intensity remain unclear. In this study, three magnetic moment configurations (MMCs) with uniaxial anisotropy, quasi-isotropy, and isotropy were established respectively to explore the effect of MMCs on the OM FMR performances in FeCoB/Ru/FeCoB trilayers with the same average compositions and geometry. No detectable FMR signal was observed in the isotropic sample, while an ultrahigh OM frequency frO of 15.91 GHz with parentheses-shaped angle distribution of FMR intensity was present in the uniaxial anisotropic sample. In contrast, a high frO of 13.29 GHz also exists in the quasi-isotropic sample, but its angle distribution of FMR intensity likes a circle, indicating an omnidirectional frO distribution. This sample is very beneficial for the OM engineering application due to its omnidirectional frO distribution, which breaks through the limitation of magnetic anisotropy to the shape design of magnetic microwave components. It can be concluded that, although three trilayers have the same compositions and geometry, completely different OM resonance performances result from the difference of MMCs, i.e. the MMC is a decisive factor for OM resonance. This study provides the design basis and optimization method for magnetic material fabrication and their device design.

Effects of Co₃O₄ Addition on Magnetic Properties of NiCuZn Ferrite Feedstock for 3-D-Printing Power Magnetic Components

Novel designs of magnetic components (inductors and transformers) lead to size reduction of power electronic (PE) systems but are difficult to be fabricated by conventional methods. Additive manufacturing can ease the fabrication of the novel designs that require intricate geometries or multi-permeability cores. The challenge is the lack of functional soft magnetic feedstock/ink with sufficient choices of different permeability or with tailorable permeability. In this study, we explored an easy way to tailor the permeability of a NiCuZn ferrite feedstock by adding different fractions of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> to the ferrite powder in the feedstock. Toroid cores were 3-D-printed using the feedstock with different fractions of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . Relative permeability of the sintered toroid cores could be tailored from 495 to 138 with 0%-0.8% of the Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . Besides, 0.5% of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> reduced the core-loss density of the ferrite by 77.6% at a low magnetic flux density of 5 mT. The effects of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> on saturation flux density, dc bias permeability, electrical resistivity, packing density, and microstructure of the sintered ferrite cores were also characterized. The mechanisms of how Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> affected the magnetic properties of the ferrite feedstock were studied.

Analysis and design of LLC resonant converter with variable magnetising inductance control

A conventional pulse frequency modulation (PFM) controlled LLC resonant converter requires a wide switching frequency operating range to regulate the output voltage. There are some disadvantages of PFM LLC resonant converters: (i) the design and optimisation of magnetic components and gate driver circuitry are challenging; (ii) due to the variable switching frequency operating range, electro-magnetic interference performance of the converter is degraded; (iii) efficiency degradation; (iv) inability to achieve independent control in multiple-output applications. To address the above-mentioned problems and achieve fixed switching frequency operation, a variable magnetising inductance control (VMIC) strategy is proposed. In the proposed VMIC control strategy, the operating switching frequency of the primary switch is fixed and the duty cycle remains constant at 0.5. At the resonant frequency operating point, the output voltage is independent of both the magnetising inductance and load. In addition, the zero current turn-off operation of the secondary rectifier requires that the switching frequency be designed below the resonant frequency. The operational principles and design considerations of the LLC resonant converter with VMIC are presented. Experimental results from a 200 W prototype are presented to validate the theoretical analysis and the effectiveness of the proposed VMIC control strategy.

Full-bridge resonant converter with hybrid control for wide input voltage range applications

This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility.

Wide voltage gain range application for full‐bridge LLC resonant converter with narrow switching frequency range

In wide voltage range applications, traditional LLC converters suffer from the following issues: (i) to cover a wide voltage gain operating range, the required switching frequency range is also large, which challenges the design and optimisation of magnetic components, gate driver circuitry, and electro-magnetic interference filter; (ii) a small magnetising inductance is preferred in wide voltage gain range application, which leads to the increase of circuit circulating current and corresponding conduction loss; (iii) passive elements are determined based on the minimum switching frequency, so bulky passive elements are required to satisfy the required operation range. To solve these problems, in this study, a full-bridge LLC (FBLLC) resonant converter with two operation modes, namely full-bridge operation and frequency doubler operation, is proposed for wide voltage gain range application. The FBLLC converter discussed in this study can be designed in half of the input voltage range when compared with the conventional method, so smaller switching frequency operating range and higher efficiency operation are guaranteed. In addition, the smooth mode transition is achieved by introducing switching frequency feedforward control and small output voltage overshoot or undershoot is observed. A 150 W experimental prototype was built to validate the theoretical analysis.

Cognitive Diagnostic Assessment of Power Supply Magnetic Components Design Based on Bayesian Network

The power electronics engineering education is aimed at helping students in becoming qualified electronics engineers. However, the existing evaluation method cannot reflect the students’ performance in knowledge-structure and skillsets objectively and accurately. To address these issues and improve the effectiveness of the current evaluation method in the field, we propose a Bayesian network model-based cognitive diagnostic assessment method and demonstrate it to evaluate students’ knowledge and skills condition with the switched-mode power supply (SMPS) magnetic components design task. The paper starts with a brief introduction to the SMPS inductor design. It continues with the Bayesian network model-based inductor proficiency model, inductor evidence model, and the task model for power magnetics volume and weight in the aerospace SMPS. Then we identify the parameters in the graded response model, relations among variables, and calculate the conditional probability between variables. Finally, we use Markov Chain Monte Carlo estimation method to get the posterior probability distribution of proficiency variables by OpenBUGS. The results show that this cognitive diagnostic assessment system can effectively reflect the students’ study performances, scientifically advise their future study plans, and effectively achieve the education goals.

Analytical Prediction Model of Energy Losses in Soft Magnetic Materials Over Broadband Frequency Range

Accurately and efficiently estimating the energy losses in electrical steels over a large frequency bandwidth, particularly in the high-frequency regimes, is of great significance for the optimal design of magnetic components. However, the traditional loss models, e.g., Steinmetz equations, have intrinsic drawbacks of being empirical and thereby require large amount of measured data to identify models' coefficients. Base on the fact that the Statistical Theory of Losses (STL) provides a simple and general method for the interpretation and prediction of the energy losses in soft magnetic materials, and conventional applications of STL are limited to low-frequency range where the skin effect is negligible, a novel broadband analytical loss model is devised by introducing the fractional derivative concept into the simulation of classical eddy current loss in both low- and high-frequency domains, and proposing the energetic model to calculate the hysteresis loss component analytically under the framework of STL. Using such model, a few measured data are required, and the solving of the coupled nonlinear diffusion problem for high-frequency loss is thereby circumvented. The simulation and experimental results confirm the accuracy and efficiency of the proposed method.

Hybrid-PWM-Controlled Current-Fed Bidirectional Series Resonant Converter With Low Current Ripple and Wide Voltage Gain

A hybrid pulse width modulation (PWM) control method for the current-fed bidirectional series resonant dc/dc converter (CF-SR BDC) is proposed in this article. In this proposed hybrid PWM control, the switching frequency is fixed to be the resonant frequency to facilitate the optimized design of magnetic components. In addition, the duty cycles of both high-voltage-side and low-voltage-side switches are also, respectively, regulated for different voltage gains. Based on this method, the CF-SR BDC is characterized by wide voltage gain, low current ripple, and high efficiency, as well as achieving soft switching for all the switches over a wide range of load. The operating principles, control method, and circuit characteristics are expounded specifically. A 160-240-V input and 400-V/1-kW output prototype was built in the laboratory, and the experimental results verify the feasibility of theoretical analysis.

A Magnetically Controlled Single-Stage AC–DC Converter

In this letter, a magnetically controlled single-stage ac-dc converter is proposed for low-power application which has the following features. First, single-stage operation is achieved by sharing switches between LLC resonant converter and totem-pole bridgeless power factor corrector (PFC) converter. Second, the power factor correction function is inherently achieved by designing the PFC converter to operate in discontinuous conduction mode. Third, the dc-link voltage is almost constant. Fourth, fixed switching frequency and duty cycle can be implemented for the switches, which simplifies the magnetic component and driver circuit design. Fifth, the LLC resonant converter is designed to operate at series resonant frequency, the highest efficiency operating point, so the converter can always achieve the maximum efficiency operation. Meanwhile, at this operating point, the converter output voltage is independent of the load so that it is functioning as a dc transformer; and finally, soft switching for all semiconductors is achieved. A 75-W experimental prototype is built to validate the proposed magnetically controlled single-stage ac-dc converter.

A Review of High Frequency Power Converters and Related Technologies

Development of power electronic converters tend to achieve high efficiency and at the same time high power density in many industrial applications. In recent years, with emerging third-generation semiconductor materials i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN), the switching frequency of several MHz has become a widely studied frequency band, therefore traditional technology can no longer meet the demand, and many new challenges appear. This paper presents a comprehensive review of high frequency (HF) converters, the essential challenges are analyzed such as topology selection, soft-switching technologies, resonant gate drivers, magnetic components design and optimization.

Single-Stage Regulated Resonant WPT Receiver With Low Input Harmonic Distortion

Resonant rectifier topologies would be a promising candidate for achieving simple, compact, and reliable single-stage wireless power transfer (WPT) receiver if not for the lack of good DC regulation capability. This paper investigates the problems that prevent the feasibility of single-stage DC regulation in resonant rectifier topologies. A possible solution is the proposed differential resonant rectifier topology, of which the rectifier is designed to have a relatively constant AC voltage, and that phase shift control is used to achieve relatively good output regulation. Design considerations on the reactive component sizing, magnetic component design, frequency and phase synchronization, small signal modelling, and closed-loop feedback control design, are discussed. Experimental results verified that the proposed WPT receiver system can achieve single-stage AC rectification and DC regulation while attaining the key features of low harmonic distortion in its AC output voltage, continuous DC current, and zero-voltage-switching (ZVS) operation over a wide operating range.

Predictive Torque Control Algorithm for a Five-Phase Induction Motor Drive for Reduced Torque Ripple With Switching Frequency Control

This article presents a progressive comparison of predictive torque control (PTC) algorithms for a five-phase induction motor fed with a two-level five-phase inverter. The extension of three-phase PTC to the five-phase motor, introduces current harmonics of the order 10n $\pm$ 3 (n = 0, 1, 2.. .), which are not responsible for torque/flux production. The inherent disadvantage of PTC is being a variable frequency algorithm, which adds complexity to the design of magnetic components. This disadvantage of PTC can be overcome by applying dwell time ( $t_{s}$ ) to the voltage vectors obtained through a minimum torque ripple condition, which is determined based on the ripple equation. In the proposed algorithm, a set of synthetic voltage vectors are generated and used for reducing flux and torque error through cost function. The use of synthetic voltage vector simplifies the cost function and further reduces the computation time. A two-step delay compensation is adopted to improve the precision of the control algorithm further. In each control cycle, an optimal switching time is calculated to reduce the torque ripple and to maintain the constant switching frequency. In this article, a modified PTC is proposed, which targets to achieve constant switching frequency, eliminate the xy-subspace current harmonics, reduce the torque ripple, and minimize the computational burden involved in the conventional predictive torque control algorithm. The experimental study is carried out on a laboratory prototype. The results show compliance with all the experimental study with different PTC algorithms with different sampling frequencies, and the modified cost function.

Analysis and Design of the LLC Resonant Converter With Variable Inductor Control Based on Time-Domain Analysis

The LLC resonant converters commonly adopt frequency modulation (FM) or combination of FM with phase-shift modulation to regulate its output voltage. However, in these control schemes, a variable switching frequency range is required, which makes the magnetic components design complicated. Therefore, in this article, magnetic control (or variable inductor control) is adopted to make the converter operating at constant switching frequency and constant duty cycle. The fundamental harmonic analysis is commonly used because of its characteristic of simplicity. However, the accuracy of this method is reduced and considerable errors occur when the switching frequency or output power changes. Therefore, an optimal design methodology based on time-domain analysis of the LLC resonant converter with magnetic control is proposed in this article. The proposed methodology can assure that the converter will operate in PO or OPO modes within the whole operating range, and zero voltage switching operation for primary switches and zero current switching operation for secondary rectifier will be guaranteed. In addition, by limiting the resonant tank root-mean-square current, the system efficiency is improved. A 200-W experimental prototype is built and the effectiveness of the proposed optimal design methodology is verified.

Investigation of Vibration and Acoustic Noise Emission of Powder Core Inductors

In power electronics applications, where the switching frequency is below the audible frequency, the design of magnetic components considering acoustic noise and vibration is as important as designing for efficiency. For the case of the powder core, which is widely used in grid-connected inverters, much research has been conducted in terms of efficiency and core loss. However, there has been limited research dealing with the topic of acoustic noise and vibration. In this paper, Sendust (Fe–Si–Al), MegaFlux (Fe–Si), and HighFlux (Fe–Ni) powder core materials, which have low magnetostriction and low core loss, are analyzed in terms of acoustic noise induced by Maxwell force and magnetostriction. Three types of powder core materials having a rectangular shape are designed for a 4-kW grid-connected inverter. Various building structures, such as rectangular, toroidal, and oval-shaped, for a Sendust core are compared with sound pressure level and efficiency. The effects of the magnetic flux density, Maxwell force, and magnetostriction are analyzed using the finite element method and are verified experimentally. In addition, the experimental results of sound pressure and inductor efficiency are presented according to core materials and building structures.

Tailoring a Silver Paste for Additive Manufacturing of Co-Fired Ferrite Magnetic Components.

Additive manufacturing (AM), or 3D-printing, has the potential for rapid prototyping of innovative designs of magnetic components used in power electronics converters. In this study, we tailored a silver paste as the metal feedstock of an extrusion 3D printer so that the metal would be compatible with a ferrite paste feedstock for 3D-printing of ferrite magnetic components. We focused on adjusting the metal formulation to match its shrinkage to that of the ferrite and to improve adhesion during the co-sintering process of the printed part. We found that a 5 wt % addition of ferrite powder in the metal paste can achieve matched shrinkage and strong adhesion. Evaluation of the co-sintered magnetic components showed no significant defects, such as cracks, warpage, or delamination, between the metal and ferrite. The shear strength between the two sintered materials was greater than 50 MPa, and the electrical resistivity of the sintered metal winding was less than twice that of the bulk silver, which is lower than those of most 3D-printed winding metals reported in the literature.

General Analytical Model for the Thermal Resistance of Windings Made of Solid or Litz Wire

In this paper, an analytical method to model the thermal resistance of windings made either of solid or litz wire is presented and validated by measurements. In addition, an extended numerical approach for litz wire windings, which also considers the twist pitch, is shown. With the presented model, it is possible to describe the thermal resistance of arbitrary wire arrangements. This approach can be used in straightforward thermal designs of magnetic devices, or it can be integrated in optimization procedures to improve the thermal designs of magnetic components. The analytical models are verified by measurements with nonpotted and epoxy-potted solid wire test setups and test setups for litz wire, which all show a good matching between the calculated and measured values. Besides the models for the thermal resistance between the winding layers, a method to simplify the thermal network of multilayer windings is presented. Finally, a thermal equivalent circuit of a test transformer has been calculated, which shows a good match between the measured and the predicted temperature distribution.

A Voltage Quadrupler Rectifier Based Pulsewidth Modulated LLC Converter With Wide Output Range

LLC resonant converter is a soft switching frequency modulated dc–dc topology with its switching frequency near the resonant frequency. However, in applications where a wide output voltage is desired, it is extremely difficult to tune its operation close to the resonant frequency. In this paper, a novel pulsewidth modulated LLC type resonant converter based on voltage quadrupler rectifier is proposed. The proposed converter always operates at the resonant frequency and is able to achieve a wide output voltage range by modulating the duty cycle of the secondary side auxiliary mosfet . This brings the benefits of the decreased circulating current and corresponding conduction loss, as well as the simplification of the parameters selection and magnetic component design. Zero-voltage-switching and zero-current-switching are realized among all power mosfet s and all power diodes, respectively. Detailed circuit operation principles and modeling method are presented. A 1.3-kW converter prototype, generating 250–420 V output from 390-V dc-link is designed. Both the circuit functionality and the theoretical analysis are verified in the experimental results.